[linux] 06/08: linux-image: prerm: Ignore version of running kernel inside a container or chroot

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benh pushed a commit to branch master
in repository linux.

commit 9f4d29bb042e6190767cdcb7b539caa2e5c79ea6
Author: Ben Hutchings <ben at decadent.org.uk>
Date:   Thu May 26 23:27:56 2016 +0100

    linux-image: prerm: Ignore version of running kernel inside a container or chroot
---
 debian/changelog                |  2 ++
 debian/templates/image.prerm.in | 25 ++++++++++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/debian/changelog b/debian/changelog
index 0bbc567..f360cf5 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -24,6 +24,8 @@ linux (4.6-1~exp2) UNRELEASED; urgency=medium
   * linux-image: Add workaround for bug #817083 in debconf
   * linux-image: prerm: Allow removal of running kernel if we can't ask debconf
     questions (Closes: #825423)
+  * linux-image: prerm: Ignore version of running kernel inside a container or
+    chroot
 
   [ Aurelien Jarno ]
   * [mips64{,el}] Set CPU to MIPS64 R2.
diff --git a/debian/templates/image.prerm.in b/debian/templates/image.prerm.in
index 2c1b8cf..df10e11 100755
--- a/debian/templates/image.prerm.in
+++ b/debian/templates/image.prerm.in
@@ -4,6 +4,7 @@ use strict;
 use warnings;
 use POSIX ();
 use Debconf::Client::ConfModule qw(:all);
+use FileHandle;
 version('2.0');
 my $capb=capb("backup");
 
@@ -43,9 +44,31 @@ if (-r "$CONF_LOC" && -f "$CONF_LOC"  ) {
 }
 
 
+# Are we in a container?  Check for $container in pid 1's environment.
+sub in_container {
+  my $res = 0;
+  if (my $fh = new FileHandle('/proc/1/environ', 'r')) {
+    local $/ = "\0";
+    $res = grep(/^container=/, <$fh>);
+    close($fh);
+  }
+  return $res;
+}
+
+
+# Are we in in a chroot?  Compare root device and inode numbers with pid 1.
+sub in_chroot {
+  my @my_root_st = stat('/');
+  my @pid1_root_st = stat('/proc/1/root');
+
+  return @my_root_st && @pid1_root_st &&
+      ($my_root_st[0] != $pid1_root_st[0] || $my_root_st[1] != $pid1_root_st[1]);
+}
+
+
 # Check to see if we are trying to remove a running kernel.
 chop($running=`uname -r`);
-if ($running eq $version) {
+if (!in_container() && !in_chroot() && $running eq $version) {
   # If we can ask debconf questions, ask whether that's intended
   # and abort if not.
   if (exists($ENV{'DEBIAN_FRONTEND'}) &&

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